Field of the Invention
The present disclosure relates to an electrophotographic member used in an electrophotographic apparatus, and a process cartridge and an electrophotographic apparatus each including the electrophotographic member.
Description of the Related Art
An electrophotographic member is used as a variety of devices, such as a developer bearing member (e.g. developing roller), a developer feed roller, a transfer roller, a charging member (e.g. charging roller), a cleaning blade, and a developer layer thickness control member (e.g. developing blade). The electric resistance of such electrophotographic members is generally in the range of 103 Ω·cm to 1010 Ω·cm.
From the viewpoint of enhancing durability, some of the electrophotographic members are provided with a surface layer.
Japanese Patent Laid-Open No. 2014-66857 discloses an electrophotographic member having a surface layer containing a polyrotaxane having a cross-linked structure in which polyrotaxane molecules each including a cyclic molecule having a functional group reactive with the isocyanate group are cross-linked to each other with an isocyanate compound having isocyanate groups at both ends thereof.
More specifically, the cross-linked structure disclosed in this patent document has a first cross-linked site formed by a reaction of one of the isocyanate groups of the isocyanate compound with the functional group of the cyclic molecule of one of the polyrotaxane molecules, and a second cross-linked site formed by a reaction of the other isocyanate group with the functional group of the cyclic molecule of another polyrotaxane molecule. According to this cited patent document, this surface layer has a higher durability than ever and, in addition, exhibits a low hardness and a low temperature dependence in a temperature range in which the electrophotographic member is used.
International Publication No. WO 2013/094127 discloses a charging member including an electroconductive surface layer containing a compound produced by chemically binding the cyclic molecule of a first polyrotaxane molecule to the cyclic molecule of a second polyrotaxane molecule. According to this cited document, the charging member is effective in reducing streaks formed in the electrophotographic image by uneven densities resulting from compression set.
The printing speed of electrophotographic apparatuses has been being increased. As the printing speed is increased, heat generated by friction between members increases, and the temperature of the members varies largely between when the apparatus is in operation and when it is not. Accordingly, it is required that electrophotographic members maintain a high durability even if it is used in still more severe environment.
The present disclosure is directed to providing an electrophotographic member that has an electric resistance unlikely to vary much in a variety of environments, and that is useful in stably forming high-quality electrophotographic images.
Also, the present disclosure is directed to providing a process cartridge and an electrophotographic apparatus that can stably form high-quality electrophotographic images.